1. Field of the Invention
The present invention relates to a laser torch for working metal workpieces, and more particularly, to a laser working torch which is provided with an air ejecting means for forming an air curtain between a laser beam converging lens and a workpiece.
2. Description of Related Art
Typically, laser working torches or devices for working or processing metal workpieces, for instance welding metal workpieces or cutting a metal workpiece, with laser beam are provided with a beam converging lens, which is supported within a housing formed with an opening through which the laser beam is directed toward a workpiece. Such a laser working device converges and directs a high energy laser beam, generated by a high power laser, such as a carbonated dioxide laser, onto a metal workpiece with a converging lens so as to melt a radiated part of the metal workpiece. One of laser working devices of this kind is known from, for instance, Japanese Unexamined Utility Model Publication No. 63-127794.
Generally, laser working devices of this kind are provided with gas injection means for injecting and directing an inert gas, such as an argon gas, toward a workpiece so as to cover a portion of the workpiece in an atmosphere of the inert gas, thereby preventing the workpiece, especially the part under working, from being oxidized.
A problem accompanying these laser working devices is that molten spatters scatter from a workpiece and stick to the converging lens. For this problem, the laser working device is typically provided with a protective glass plate, which in turn is positioned between the converging lens and a workpiece, and an air injection means by which an air curtain is formed so as to expand and intersect an axis of the laser beam at an approximately right angle. Through the use of the protective glass plate and air curtain, the converging lens is protected against scattering molten spatters.
Although there is no interference between an inert gas and an air curtain, however, the air curtain approximately perpendicularly intersecting the laser beam easily allows molten spatters scattering toward the converging lens to pass therethrough. In order to prevent molten spatters from passing through the air curtain, it is suggested that the air injection means must inject air at a high pressure. However, in this instance, a highly pressurized air curtain causes a negative pressure therearound, so as to generate a problem that molten spatters scattering from a workpiece more easily pass through the air curtain. These molten spatters passed through the air curtain stick to the protective glass plate. Thus, one needs to clean up the dirty protective glass plate or to replace the dirty protective glass plate with a new one, either alternative being undesirable.